Nyko today announced that they will release the Cord-Free wireless adapter for the Wii Nunchuk this February. Here is more info:

"While the highly anticipated award winning Wireless Nunchuck for Wii is a brand-new standalone product, the Cord-Free wireless adapter for Wii Nunchuk differentiates from its sibling by converting your standard wired Nunchuk into a wireless peripheral. The adapter adds a convenient self-standing sleeve for the wired Nunchuk and a wireless signal dongle to the bottom of your Wii Remote. A small dongle provides lag-free wireless connection between your Wii Remote and Nunchuk and adds up to 15 feet of wireless range. The self-standing Nunchuk sleeve features a convenient compact cord management system keeping the existing Nunchuk cord organized and out of site. The Cord-Free wireless adapter for the Wii Nunchuk runs on two AAA batteries (included) and provides up to 60 hours of continuous gameplay.